Studies on cytoplasmic cAMP-dependent protein kinases have the following goals: (1) Purify and characterize cyclic AMP-dependent protein kinases from bovine brain; (2) Correlate physicochemical properties of types I and II protein kinases with their regulation and function; (3) Determine those alterations in secondary, tertiary and quaternary structure of protein kinases involved in cyclic AMP-binding, subunit dissociation, autophosphorylation, catalysis, and folding of subunit polypeptides; (4) Characterize the structure and environment of the cyclic AMP-binding and catalytic sites. Enzymes will be purified by conventional, hydrophobic and affinity techniques and studied by kinetic, physicochemical, spectroscopic and photoaffinity-labelling methods. The objectives of research on membrane-associated protein kinase are: (1) to assess the possibility that protein kinase provides a flexible, cyclic AMP-regulated system capable of modifying membrane structure and function; (2) to determine whether membrane constituents other than cyclic AMP may regulate interactions between substrates and protein kinase; (3) to determine if non-substrate membrane proteins may influence the activity of protein kinase; (4) to solubilize and characterize membrane-associated protein kinase and determine the relatedness of soluble and particulate kinases; and (5) to utilize the methods and concepts derived from the erythrocyte membrane model system in studying the roles of cyclic AMP and protein kinase in more complex cells, such as brain cells, neural and glial tumors cells. Methodology pertinent to this research includes: use of specific enzymic and chemical probes (e.g., photoaffinity labelling) of membrane structure, selective detergent solubilization of membrane components, polyacrylamide electrophoresis and membrane preparation and characterization.